MALCOLM Turnbull's majority government is under threat after the shocking revelation that Deputy Prime Minister Barnaby Joyce may be a dual citizen.

The Nationals leader made the announcement in Parliament this morning that he will refer his own eligibility to sit to the High Court.

Mr Joyce told the lower house he would remain in his position until the matter was resolved.

He said he was shocked to learn he could be a citizen of New Zealand by descent via his father.

Last Thursday afternoon the New Zealand High Commission contacted me to advise that on the basis of preliminary advice from their department of internal affairs which had received inquiries from the New Zealand Labor Party they considered that I may be a citizen by descent of New Zealand," Mr Joyce told Parliament.

"Needless to say I was shocked to receive this information. I have always been an Australian citizen, born in Tamworth, just as my mother and my great-grandmother was born there 100 years earlier.

"Neither I, nor my parents, have ever had any reason to believe that I may be a citizen of any other country."

Australian Deputy Prime Minister Barnaby Joyce may be a New Zealand citizen.AAP Image / Lukas Coch

The Government holds a one seat majority in the House of Representatives and if Mr Joyce were disqualified from being able to sit in Parliament, the government would lose its majority.

His father James Joyce was born in Dunedin, NZ before moving to Australia.

Mr Joyce said the government believed, based on advice from the Solicitor General, that he would not be disqualified from serving as the Member for New England.

There are also fresh questions over the citizenship status of Labor MPs, including deputy leader Tanya Plibersek and Anthony Albanese.

It comes after two Greens senators resigned over holding dual citizenship, and Nationals MP and Cabinet Minister Matt Canavan and One Nation Senator Malcolm Roberts were referred to the High Court.

In July, Mr Turnbull said the Greens showed "sloppiness" by falling foul of political rules around citizenship.

At the time he said: "It is pretty amazing, isn't it, that you have had two out of nine Greens senators didn't realise they were citizens of another country. It shows incredible sloppiness on their part".

The Prime Minister has today written to Opposition Leader Bill Shorten to invite him to "nominate any Labor members of senators whose circumstances may raise questions".

The Prime Minister has written to the Opposition Leader over Section 44.Source:Supplied